1. Bring a large pot of salted water to a boil. Add the pasta and cook it to al dente according to the package directions. When it's done, remove a cup of the pasta water and set it aside. Drain the pasta but do not rinse it.

2. While it's cooking, heat the olive oil in a large skillet, such as a 10-inch cast iron skillet, over medium-high heat. Add the sausage and 2 teaspoons of Cajun seasoning and cook until crisp on both sides, about 5 minutes. Transfer to a clean plate or bowl.

3. Turn the stove down to medium heat and add the onion and pepper, the remaining teaspoon of Cajun seasoning, and a little bit of red pepper flakes to the same skillet and cook until softened, about 3 minutes. Add the garlic and cook for another minute, until fragrant.

4. Whisk in the chicken broth, heavy cream, and tomato paste until smooth. Bring the mixture to a gentle boil over medium-high heat, then reduce the heat to medium-low and simmer for 5-7 minutes to thicken slightly.

5. Stir in the Parmesan cheese, then add the cooked pasta and crispy sausage and toss to coat. Add a splash of the reserved pasta water as needed until the sauce is glossy and coats the noodles well. Serve right away with more Parmesan cheese and fresh parsley.